Extraction process



EXTRACTION PROCESS Filed may 26, 1930- .KlYnH E w w 0^/ M p .K C :l .5 C/

0 00% O O OO oo 0 o 0 o0 o 0 a OOO O O OOOO AAI C O O O D,V N\OO ../Q. 0 ff m L Z A A v A o o 51V oww 0` P 000.00000 .AM o, 00o. OO O O O 5 Patented Dec. 3, 19.35 u

A UNITED STAT Es PATENT OFFICE;

illem Johannes Dominicus van Dijck, The Hague, Netherlands, assigner to Shell Devel-l opment Company,` San Francisco, corporation of Delaware Calif., a

. Application May ze, 193e, serial No. 455,959 In the NetherlandsJuneS, 1929 1 2s claims. (o1. 19e-1s)- My invention vrelates to a process of separating a mixture of liquids into its components.

`Zltisold toseparate such mixtures-by rectican tion. Advantage is taken of the fact vthat the 5 vapour of a mixture of liquids has a composition which in general Adiffers from that of the liquid withl vwhich it is in equilibrium.l By, a suitable application ofthe principle of counter-current flow of the vapour and liquid phases it is theoretically possible to obtain the various components in a pure state; in practice the theoretically possible result can be approximated only. Heating and cooling play an important .part in'this process. lIt has already been proposed to extract from a mixture of liquids by means of one liquid solvent or a mixture ofliquid solvents one component or a group'of components. Thus, for instance, it is a general practice in petroleum technology to subject certain petroleum fractions'to a treatment with liquid SOz, whereby a group of aromatic constituents is dissolved rin the SO: and can be removed thereby. This and similar processes are, however, not feasible in that it is impossible thereby to attain a completey separation'of the lead to a true rectiiication.

Now the process according -to the present in- `vention is based upon the discovery that a true fractionation is quite possible if instead of one, at least two, liquid solvents are used simultaneously. The liquid solvents are conducted counter currently with respect to each other and are so various components, in other words they do not A than in B or vice versa. -But if Ra is more soluble in Bthan is R1, a method of fractionation is providedaccording to the present invention. Therefore, with regard tothe partition ratios",

-it is' ssentialthat these valuesbe different in 5 order. to eiect a fractionation of a mixture of liquid components. As is well known; a solute will distribute itself between two contacting nonlmiscible solvents at any vgiven temperature Ain chosen that they are as far as possible mutuallyV f non-miscible, whilst further, the proportions in which the various components or groups oi components to be removed from the mixture are soluble in the two liquid solvents, preferably should differ as much-as possible. In other words, the underlying principle of the present invention is components by subjecting the mixture vto the influence of two substantially non-miscible liquid solvents, owing in contact with the said mixture of liquid components and counter currently with respect to each other, the components or groups of components having different partition ratios".

with respect to the two solvents.

, To illustrate thijs proposition, the separation ot R1 from a mixture`l consisting of R1 and Rz by' flowing the solvents A and B counter currently in the mixture, may be described by Vway oi' exempliiication. As 4a preliminary observation, it is rst pointed out that R1 as well as Rn may be miscible with A in all proportions. Both may b e '55- also solublein B. Both may be'more soluble in that it is possible to fractionate a mixture Aof liquid accordance with the .following general equation 10 where Am is the concentration of the solute R1 15 in the solvent A, Bm is the concentration of R1 in the solvent B and K1 is a constant, commonly referred to as a partition ratio".

'Similarly another solute R: will obey the followingI relation: so

where A'az is the concentration of Rz in A and Baz is the. concentration of Ra in B, and K2 is the lZ5 partition ratio. Now in accordance with the u present invention it is essential that the values K1 and K2 be diier'ent. As used in the claims the term partition raticihas the significance indicated above, viz.; the concentration ratio of a 30 gravities of the liquid solvents is not, however, anv

essential factor, s ince the said solvents can also be passed adjacent to each other without making use of lgravity, e. g. by conducting the two liquids separated by a diffusion membrane adjacent to each otherin a horizontal direction. `'1"he func'- tion of the diffusion membrane is merelyme- -V chanically to separate the streams of liquids. The molecules of all the liquids are, however, able to pass freely through the said diusion mem- 50 brane. The modification oi' the invention in which'th'e, liquids are conducted adjacent to each lother is illustrated in Figure 1 of the accompanying drawing in which A and B are the liquid solvents, R is `the mixture to be separated, R1 and R3 A.55H

30. up to each of the liquid solvents A and B the com- -applied continuously or intermittently, and an illustration o! each of these two forms will now be given with reference to Figures 2 and 3 of the According to the continuous form ofthe process the mixture runs successively through a number A entrance, modified by the action of the liquid l0 solvents, and returned to the reservoir. 'Ihe fact of separators, in which each time one of the components or a group of components is separated. y One of these separators is shown in Figure 2 of' the drawing in which S is the separator or scrubbing tower,-A is the liquid of lower specic gravity and Bthe liquid of higher specific gravity, P the 'surface oi separation of the two liquid solvents A' and n, R the mixture to be split up and R1 and R1 the groups of components to be removed respectively by the liquid solvents A and B. For this purpose the mixture to be split up R may be conducted at a'suitably chosen level to a vertical scrubbing tower S filled with a liquid. 'I'he lling of the scrubbing tower originally consists of the two immiscible or practically immiscible liquid solvents A and B obtained by introducing at the top oi' the scrubbing tower the one, and at the bottom the otherliquid solvent of lower specific gravity. Now, for instance, when the mixture to be separated into its components is conducted intothe scrubbing tower in the middle, it will give ponents or groups of components R1 and R2 insofar as they are soluble therein. During thev passage of the liquid solvents through each other the mixture to be separated is divided into two After the heaviest liquid solvent B has passed through the scrubbing tower, -it is withdrawn at the bottom together with the component or groupof components dissolved therein. Outilowing liquid indicated in Figure -2 by B-i-Rn will contain little or no Ri, because the stream of A, which vconstantly rises through the stream ofB-l-Rz flowing out at the bottom of the tower S, will continuously wash the component R1 from the down ilowing stream, because R1 is more soluble in A than B. Should the liquid flowing out at the bottom of the tower S show any trace of R1, this tendency can be eliminated by increasing the stream of liquid solvent A. In like manner, the liquid solvent of lower specific gravity A is withdrawn at the top of the scrubbing tower with' the component or components dissolved therein. The liquidl solvents may then be separated from the' components dissolved thereby by distillatiomrectiflcation, freezing or in some other known physical or'chemical manner and the liquid solvents thus regenerated can again be circulated. After one desired pure component or group, forexample R, has thus been removed, the

residue R2 which is further separated into the components it contains, i. e. the original mixture deprived of the said pure component or group R1 andt with or without the second liquid solvent'B,

lis then conducted to similar scrubbing towers, in which it is subjected in like vmanner to the action of the same orother liquid solvents, the separation ofthe mixture thus being ultimately completed. According' to the intermittent form' of the process the desired pure components or groups arel .separatedfrom a certain quantity of mixture in one and the same apparatus. In this case there is no continuous feed of the mixture to be split up,this being fed in bulk into areservoir if desired simultaneously with a quantity of one of vliquid from the reservoir 'can be pumped into the tower at lsome point, and then drawn off again sometimes containing some of the liquid solvents at some point in close proximity to the point of that a portion of the liquid solvents may be drawn of! together with the modied initial liquidwill, however, not disturb 'the' extraction process, since such liquids depending upon' their l5 speciiic gravity will either sink or risefand can be subsequently removed.-

The content of the scrubbingtower is thus, in effect, enlarged at the point of contact by that of the reservoir, so that the mixture as a whole 20 comes into contact with the liquid solvents; the

' various components or groups of components are thus separated Afrom the mixture in the selected liquid solvents, e'. g. by a regulation of the'velocity o f the liquid solvents according to the'solubility 25 of the components or groups of components to be separated, drawn off with the respective liquid solvents and further treated as described in the continuous method. The top, the bottom or an intermediate point of the scrubbing tower can 80 be chosen as the point of contact between tower and reservoir. In the rst case the components are successively drawn oi at the bottom, in the second case at the top. In the third case comor groups removed by the C and D respectively,

E is the reservoir and S the separator or scrubber.

In operating according to this form of the process the mixture R to be separated together with some of the liquid solvent C is brought into the scrubber S in which the liquids C and D are passing through each other, the liquid C of higher specific gravity being introduced at the top of the scrubber and the liquid D oi lower specific gravity at the bottom thereof. The mixture R and C having been acted upon by the liquids in the scrubber S is then returned to the-reservoir E. By carefully regulating the quantities of C and D and by maintaining a predetermined pumping velocity of the mixture R+C, only R1 is removed by the liquid solvent C, because although Ra `is substantially soluble in C the solubility of Rz in D is still greater and'by carefully regulating the quantity ci' D which runs through the tower S even the last traces of R2 will be removed by the ascending liquid D. Since, however, only a limited quantity of the mixture R is present in the scrubber S it will take several hours before the total quantity has been circulated and the component R1 removed. During this period the component R1 is gradually removed, while at the 7o same time some of R2 is removed by D at the top aoeaioe I'he possibility is, however, not excluded that iinally the components R1 and Rz may be again further separated possibly even with the samel liquid solvents but under different conditions.

IfA a single combination of liquid solvents does l5 R1 and R2 of similar components not yet separated canrbe subjected tothe action of otherv liquidv solvents in a second apparatus.

A good idea of the procs according to the in- .vention can be obtained by comparing it with that taking place in a rectifying column. In the present process, instead of the vapour phase, which differs in composition from the liquid phase. there arises a second liquid phase, likewise differing from the first with regard to the concentration of the components to be separated. As in the caseof` rectification, the degree of separation is governed by the extent of the contact surface between the two phases, the quantities of the phases .passed through per'unit `of time, and the mutual proportions thereof, as also by the measures taken in order to prevent components once separated, being again mixed with each other. An essential point of difference is, however, that in the process according to the invention; separation depends on the diierence in solubility of the components to be separated' instead of a diierence in volatility, and as a result the process is more flexible, and it is possible 4D by varying the choice of the liquid solvents to carry out the separation in variousmanners- Finally, it should be noted that as one of the liquid solvents a component or group of components already present in the mixture to be separated may be used, and also that it is not always necessary to pass the two liquid solvents in countercurrent throughout the whole length of the tower.

Since my invention is a basically novel method oi' fractionation, it may be carried into practice without any limitation as to the mixtures to be, split up or the auxiliary liquids to be employed, which latter should be determined by practical experiments in any given case. However, in order to illustrate my invention more fully with regard to the auxiliary liquids to be employed I may say that mixtures of hydrocarbons, especially ofthe heavy type such as lubricating oils may be fully fractionated with the aid of benzine and liquid vsulphur dioxide according to my inventionlas described hereinbefore. Mixtures of lighter hydrocarbons such as for example lamp oil,gas oil, light lubricating fractions etc. may .be fully fractionated with methyl alcohol and carbon disulphide.

The term fractionating as used in the claims means the process of separating the various components or groups of components of the original` 70 mixture of liquid components from each other, or in other words, it means simply the process of resolving the original mixture into its component parts, so as to obtain pure substances or groups of closely related substances.

The terms a component or a pure compo'- not bring about a suicient separation, the groups nent as used in` the claims include pure substances and a group of closely relatedtsubstanoes. I

What I claim is: p 1. A process of fractionating a mixture of liq` uid components whichl comprises subjecting the o.

said mixture to the action of two counterilowing mutually non-misciblegli'quid solvents, the said solvents being so selected that the components of the liquid mixture -have different partition ratios with respect to the said solvents and recovering l0 'the said solvents containing at least partially fractionated components of the original mixture;

2. A process of fractionating a mixture of liquid components which comprisessubjecting the said mixture to the action of two counter'owing l5 mutually non-miscible liquid solvents of diierent specific gravities, the said `solvents vbeing so selected that the components of the liquid mixture have diierent partition ratios with respect to the said solvents and recovering the said solvents 20 containing at least partially fractionated compo- .nents of the original mixture.

3. A process o f fractionating a mixture of liq-v. uid components. which comprises subjecting the Y said mixture to the action of two counterilowing 25 mutually non-miscible liquid solvents of difierent specic gravities, one of said liquid solvents being miscible with the said mixture, the said solvents being so selected that the components of the liquid mixture have different partition ra- 80 tios with respect to the said solvents and recovering the said solvents containing at least partially fractionated components of the original mixture.

4. A process of fractionating a mixture of liq- 35 uid components which comprises subjecting the said mixture to the action of two counterilowing mutually non-miscible liquid solvents of different specific gravities, both of said solvents being mis-. cible with the said mixture, the said solvents be- 40 ing so selected that .the components of the liquid mixture have diiferent partition ratios with respect to the said solvents and recovering the said solvents containing at least partially fractionated components'of the original mixture.

5. A process of fractionating a mixture of liquid components which comprises subjecting the l said mixture to the action o'f two counterflowing mutually non-miscible liquid solvents, one of the liquid solvents having a greater dissolving action 50 than the other of said liquid solvents for at least one of the components of the said mixture of liquid components, in such a manner that-one of the solvents containing components of the original mixture oi.' liquid components encounters the 55'- other solvent in substantially pure state. whereby the second named solvent progressively extracts one component `from the first named solvent, until at least one solventv contains only one pure component of the original mixture of liquid coni- 00 ponents, and-separately recovering the said solvents, one of which contains a substantially pure component of the original mixture of liquid components.

6. A process of fractionating a vmixture of liquid components which comprises subjecting the said mixture to the action of liquid solvents'by forcing two mutually non-miscible liquid solvents to flow adjacently and countercurrently to e ch other in a confined body of the said liquid mxture, one of the liquid solvents having a greater dissolvingaction than the other of said liquid solvents for at leastone of the components of v the said mixture of liquid components, in such a liquid phases are formed when one of said .solvents is added to a homogeneous liquid phase containing oil and the other solvent.

21. In a solvent extraction process for separating a mixture of liquid components into two portions by means of two at least partially immiscible solvents, which when mixed with the said mixture form separate layers, the steps of introduc-` solvents intov an' extraction zone at different points,

thereof, counterowing the two solvents within the extraction zone between the said points, and subjecting the said mixture to the extractive action of the said counterowing solvents by introducingit into the extraction -zone at a point between said two points;

23. In a solvent extraction process for separating a mineral oil containing paraiiin'ic and naphthenic constituents into fractions respectivelyy more parafnic and more naphthenic than the original oil by means of two solvents, each of' which when brought into contact with the oil selectively dissolves one of said constituents, the steps of introducing the two solvents into an extraction zone at different points thereof, counterflowing the two solvents within the extraction zone between the said points, and subjecting the said oil to the extractive action of the said counterflowing solvents by introducing it into the extraction zone at a point between said two points.

24. In the extraction process for separating a liquid mixture into two portions by means of two solvents adapted to form separate layers when in contact with each other, one of said solvents having a greater solvent power for one portion of the mixture and the other of said solvents having a greater solvent power for the other portion of the mixture, the steps of introducing the two solvents separately into an extraction zone at diierent points thereof, counterlowing the two solvents within the extraction zone between the said points, one of the solventspassing only through a portion of the extraction zone, and subjecting the said mixture to the extraction action of the said counterowing solvents by introducing it into the extraction zone at a point between said two points. i

25. .In the extraction process for separating hydrocarbon oil into two portions by means of two solvents adapted to form lseparate layers when in contact with each other, one of said solvents having a greater solvent power for one portion of the oil and the other of said solventsha'ving a greater solvent power for the -other portion of -the oil, the steps of introducing the two solvents separately into-an e'xtractionzone at diierent points thereof, counterowing the two solvents within the extraction zone between the said points, one of the solvents passing only through a portion of the extraction zone, and subjecting the 5 said oil tothe extraction action of the said counterflowing solvents by introducing it into the extraction zone at a point between said two points. i

26. In asolvent extraction process for separating a mixture of liquid components into two por- 10 tions by means of two at least partially immiscible solvents which, when mixed with said mixture, form separate layers, the steps of introducing the two solvents into an extraction zone at different points thereof, counteri'lowing the two sol- 15 vents within the extraction zone between the said points, subjecting the said mixture to the extractive action of the said counterflowing solvents by introducing it into the extraction zone at a point between said two points, and withdrawing at least 20 one of the solvents and components dissolved therein from the extraction zone at a point adjacent tothe pointyof introduction of the other solvent.

27. In a solvent extraction process for separat- 25 ing a hydrocarbon mineral oil mixture into two portions by means of two at least partially immiscible solvents which, when mixed with the hydrocarbon mixture, form separate layers, the steps of introducing the two. solvents into an extrac- 30 l tion zone at different points thereof, counteriiowing the two solvents within the extraction zone between said points, subjecting the said hydrocarbon mixture to the extractive action of the said counteriiowing solvents by introducing it into 35 the extraction zone at a point between said two points, and withdrawing at least one of the-solvents and components dissolved therein from the extraction zone at a point adjacent to the point of introduction of the other solvent.

28. In a solvent extractionF process for separating a hydrocarbon mineral oil mixture into two vportions by means of two at least partiallyrimmiscible solvents which, when mixed with the hydrocarbon mixture, form separate layers, the first 45 of said solvents being a selective solvent for certain components of said hydrocarbon mixture, and the second solvent being'capable of dissolv- .ing other components of said hydrocarbon mixture, the steps of introducing the two solvents into 50 an extraction zone at different points thereof, counterfiowing the two solvents within the extraction zone between said points, subjecting the said hydrocarbon mixture to the extractive action of the said counterflo'wing solvents by introduc-'` ing it into the extraction zone at a point between said two points, withdrawing said iirst solvent and components dissolved therein from. the extraction zone at a point adjacent to the point of introduction of said second solvent, and withdraw- 60 ing the said second solvent and components dissolved therein from the extraction zone at a point adjacent to the point of introduction of said ilrst solvent.

L 65 WILLEM JOHANNES DOMINICUS VAN DIJCK. 

